Characteristics of printed Thai characters (also called the Siamese characters) that notate the Thai language will be described with reference to FIG. 1. FIG. 1 illustrates a specific example of printed Thai characters, and printed single-columns 101 to 106 that will be explained below are described in FIG. 1.    (a) The printed single-column 101 is a printed single-column that includes two characters printed in the third and fourth rows.    (b) The printed single-column 102 is a printed single-column that includes two characters printed in the second and third rows.    (c) The printed single-column 103 is a printed single-column that includes three characters printed in the second, third and fourth rows.    (d) The printed single-column 104 is a printed single-column that includes three characters printed in the first, second and third rows.    (e) The printed single-column 105 is a printed single-column that includes a single character printed so as to bridge the third and fourth rows.    (d) The printed single-column 106 is a printed single-column that includes a single character printed so as to bridge the second and third rows.
Printed Thai characters, including the above specific examples, possess the three characteristics listed below.
1) Each printed single-column included in a text line is formed of four rows. In the following explanation, these “rows” will be called “printed rows” as appropriate.
2) Each Thai character is basically printed in one of the printed rows, but some exceptional characters are printed in a plurality of printed rows, so as to bridge the third and second rows or the third and fourth rows.
3) A printed single-column includes at most three Thai characters. In addition, the third row always contains any given character. In other words, a printed single-column absolutely includes a character printed only in the third row or partially printed in the third row.
Because of the above three characteristics, when the Thai language is printed, an actual spacing may not be created evenly between the current text line and the text line preceding the current text line by characters printed in the two text lines. Here, the actual spacing refers to a space on a print medium (paper, display device, etc.).
The above uneven space will be explained with reference to a specific example in FIG. 2. As illustrated in FIG. 2, the actual spacing between the second preceding text line (first text line) and the preceding text line (second text line) is equal to a preset text line spacing. However, if no characters are contained in the fourth row of the preceding text line (second text line) and no characters are contained in the first and second rows of the current text line (third text line), the actual spacing between those two text lines becomes much larger than the preset text line spacing.
By eliminating or decreasing such wasted spaces, the consumption of printed paper can be reduced. If a medium is a display device, the number of characters displayed on the screen can be increased. Patent literature 1 describes an exemplary technique for decreasing space parts between text lines by making use of the characteristics of the Thai language, reducing the consumption of printed paper.
The technique described in Patent literature 1 divides each print text line for the Thai language into three rows, or upper, middle and lower parts, and prints these parts separately from one another upon printing.
When a print text line is divided into the three parts, or the upper, middle and lower parts, as described above, they are typically printed so that the upper and lower parts have the same height as the middle part. In fact, however, characters printed in the upper and lower parts have a shorter height than those printed in the middle part. Accordingly, the technique described in Patent literature 1 focuses on the point that the upper and lower parts each contain a larger vertical space. Specifically, the technique described in Patent literature 1 decreases the heights of the upper and lower parts to about half that of the middle part by cutting out space parts when printing the upper and lower parts. In this way, the height of each text line is decreased from three times (upper part+middle part+lower part) to about two times (upper part with about halved height+middle part+lower part with about halved height) the height of the middle part. It is thus possible to decrease the height of each text line.